An evaluation of potential material±coolant compatibility for applications in advanced fusion reactors T. Kondo a , Y. Watanabe a, * , Y.S. Yi a,1 , A. Hishinuma b a Faculty of Engineering, Department of Machine Intelligence and Systems Engineering, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan b Japan Atomic Energy Research Institute, Tokai-mura, Ibaraki-ken, Japan Abstract In assessing possible potential issues for fusion applications, the compatibility of several metallic structural materials was examined using high temperature/pressure steam as test environment. High corrosion resistance associated with protective oxide ®lm formation was regarded as essential for the function of protecting from tritium permeation and corrosion damage. A Ti±Al-based intermetallic compound with V addition, recently developed, showed excellent performance. A low-activation ferritic/martensitic steel, F82-H, was comparable with the current advanced materials for modern supercritical fossil boilers, while some potential vanadium alloys, although not intended for use in steam, were found less compatible. Ó 1998 Elsevier Science B.V. All rights reserved. 1. Introduction 1.1. Background Materials programs in the basic research phase are not always aware of the issues in ultimate service re- quirements. Before evolving into an engineering phase, speci®c reactor design windows must be referred to. For a reactor designer, the current choice of a material- coolant system is con®ned in the following sets of combinations [1]: Common issues in energy systems design are the needs of higher service temperatures and lower failure risks. These requirements are generally contradictory to each other, unless either the material, coolant or their combined behavior are improved. Then what option can really be potential at the moment? Engineering experience indicates that the issues of chemical compatibility as well as mechanical strength are among the most critical. Radiation eects are con- nected with those properties, but the eects themselves are generally less strictly handicapped by temperature shift. In the chemical compatibility aspect, ferritic/mar- tensitic steels can be compatible with water at light water reactor operating temperatures. However, at tempera- tures above 647 K (374°C), the critical point for liquid water, one can pick only helium, unless superheated steam is considered. Vanadium alloys have potential for higher operating temperatures in conjunction with liquid metal coolants. For materials in the pre-engineering stage, such as SiC composites and Ti±Al, coolant se- lection is still premature. 1.2. Objectives An experimental evaluation was carried out of the compatibility of some candidate fusion structural Materials Coolant  Austenitic steels,  Ferritic/martensitic (F/M) steels,  Liquid (Water, liquid metal/e.g., lithium)  Vanadium (V) alloys,  Ceramics and their composites,  Gas (helium)  Intermetallic compounds Journal of Nuclear Materials 258±263 (1998) 2083±2087 * Corresponding author. Tel.: +81-22-217-6896; fax: +81-22- 217-6895; e-mail: yutaka@rift.mech.tohoku.ac.jp. 1 Present address: University of Michigan, Ann Arbor, MI, USA. 0022-3115/98/$19.00 Ó 1998 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 3 1 1 5 ( 9 8 ) 0 0 3 4 4 - 4